The research programs of the principal user group span the fields of neuroanatomy, cell biology, dermatology and reproductive biology. These programs rely on the use of transmission electron microscopy to: (1) localize ferritin labeled luteinizing hormone and luteinizing hormone receptors labeled with receptor antibodies by immunohistochemistry, (2) map structural and functional sites on isolated luteinizing hormone receptors with ferritin labeled receptor antibodies (3) map microvasculature and elastic fibers in human skin by serial reconstruction and immunohistochemistry, (4) examine effects of estrogen on hypothalamic cell ultrastructure in relation to age-related reproductive failure, (5) examine hypothalamic neuroendocrine connections related to the control of gonadotropin release by ultrastructural tracing methods and immunohistochemical detection of transmitters and hormones, (6) determine the origin of "LHRH-like" peptide in the ovary by immunohistochemistry, (7) examine the effect of sex steroids on developing and adult mammalian spinal motoneurons and identify neurons by immunohistochemistry that input to motoneurons labeled by intracellular injection of horseradish peroxidase and (8) examine the effect of ovarian steroids on the hypothalamus, preoptic area and uterus by assessing neuronal and membrane ultrastructure and gap junction formation (uterus). These projects are supported by NIH grants. Other projects, such as study of membranes in embryo development and localization of antigens in ovarian autoimmune failure, are also being developed and preliminary explorations conducted. Our current electron microscope, which is over 15 years old, is outdated, difficult to repair and unreliable and no longer supports the research needs of our group. We are requesting a Philips 410LS transmisssion electron microscope and Barry Control vibration isolation equipment that will be situated within the darkroom-microscopy facility in the Department of Obstetrics and Gynecology. A new microscope will allow us to conduct our research on a routine basis.